﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Data;
using System.Windows;

namespace AppToolkit.WPF.Controls
{
    /// <summary>
    /// Outputs native xaml format.
    /// </summary>
    [ValueConversion(typeof(string), typeof(string))]
    public class NullConverter : IValueConverter
    {
        #region IValueConverter Members

        /// <summary>
        /// Converts a value. 
        /// </summary>
        /// <returns>
        /// A converted value. If the method returns null, the valid null value is used.
        /// </returns>
        /// <param name="value">The value produced by the binding source.</param><param name="targetType">The type of the binding target property.</param><param name="parameter">The converter parameter to use.</param><param name="culture">The culture to use in the converter.</param>
        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            string textValue = value as string;
            if (textValue != null)
            {
                return textValue;
            }
            return DependencyProperty.UnsetValue;
        }

        /// <summary>
        /// Converts a value. 
        /// </summary>
        /// <returns>
        /// A converted value. If the method returns null, the valid null value is used.
        /// </returns>
        /// <param name="value">The value that is produced by the binding target.</param><param name="targetType">The type to convert to.</param><param name="parameter">The converter parameter to use.</param><param name="culture">The culture to use in the converter.</param>
        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            string xamlValue = value as string;
            if (xamlValue != null)
            {
                return xamlValue;
            }
            return DependencyProperty.UnsetValue;
        }

        #endregion
    }
}
